The invention relates generally to transmissions and, more particularly, to a hydro-mechanical continuously variable transmission for producing high torque output.
Transmissions are used in agricultural and construction equipment to transmit power from power sources, such as internal combustion engines to equipment for accomplishing a desired task. For example, transmissions are used to properly transmit power to the wheels of a vehicle, or to a vehicle implement. A continuously variable transmission (CVT) is a transmission that can change through an infinite number of effective gear ratios between a minimum and maximum range. In contrast, non-CVT transmissions offer a fixed number of gear ratios. Specifically, hydrostatic CVTs may use a variable displacement pump and a hydraulic motor and transmit power using hydraulic fluid. A swash plate may be used within the variable displacement pump to vary the output of the hydrostatic CVT by adjusting the fluid flowing into the hydraulic motor. Thus, the swash plate may enable the hydrostatic CVT to be continuously variable. Some hydrostatic CVTs may be combined with gear assemblies, drive shafts, and clutches to create a hydro-mechanical CVT. It may be appreciated that in certain applications, such as in construction equipment, a high torque output may be utilized by implements of the construction equipment. Further, a high torque output may be beneficial for low speed movement of vehicles, such as construction vehicles or agricultural vehicles. However, hydro-mechanical CVTs may provide start up torque inefficiently for such applications.